Design, fabrication and characterization of organic-inorganic hybrid solar cells

• Main Author: Ahmed Ali Said Ahmed
• Other Authors: Zhang Qichun
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Materials
• Online Access: https://hdl.handle.net/10356/136893
• Institution: Nanyang Technological University

Firstly, electron transporting materials have a critical role in achieving high power conversion efficiency in perovskite solar cell. High synthesis temperature of metal oxides as electron transporting materials hinders flexible solar cell technology and consumes huge energy. Thus, switching to organic electron transporting materials for low-temperature processing and energy-saving is necessary and highly-desirable. However, phenyl-C61-butyric acid methyl ester (PCBM) as a conventional electron transporting material lacks the tunability of frontier molecular orbitals, as well as its poor stability and high price, inspired scientists to explore novel organic electron transporting materials, which have been considered as good candidates to substitute PCBM. Organic transporting materials are distinguished by low synthesis price, tunable frontier molecular orbital, easy of film forming and stable toward air. Organic transporting materials can be classified into organic small molecules and N-type conjugated polymers. Secondly, lead-based perovskite solar cells achieved high performance. However, its toxicity and instability encourage scientists to develop stable and ecofriendly lead-free solar cells. This project was designed to develop novel organic electron transporting materials, which can push inverted perovskite solar cells to high stability and high-power conversion efficiency. Developing stable and efficient lead-free solar cell is the second aim of this project. Thus, this thesis addresses the design, synthesis and characterization of novel organic transporting materials. Furthermore, they have been investigated as electron transporting layers in inverted perovskite solar cells. Importantly, this thesis also addresses the possibility of replacing lead-based solar cells with stable and efficient lead-free solar cells. Introduction on the research of organic electron transporting materials and lead-free solar cells is involved. The rationale, hypothesis and objectives are presented. Moreover, the strategies, methods and approaches to achieve the objectives are discussed in each chapter. The literature review on recent progress of organic transporting materials in perovskite solar cells is provided, which includes the classification of organic transporting materials according to their building block, the effect of their structure on their performance as electron transporting layer is included. Moreover, the literature review provides the information about different types of lead-free solar cells and their advantages and their drawbacks. The achieved findings in this thesis include the following: (1) Six NDI-based molecules have been designed and synthesized as electron transporting layers in inverted perovskite solar cells; (2) Two pyrene-based molecules were designed and synthesized as electron transporting layers; (3) The effect of sulfur position in pyrene-based molecules was investigated (4) Three N-type conjugated polymers were explored as electron transporting layer (5) The effect of embedded sp2-nitrogen in donor and acceptors of conjugated polymer was explored and (6) Tellurium tetraiodide was explored as a promising light absorber in solar cells. Finally, summary was provided, as well as the recommendations for current and future work were involved in last chapter.